Dry spinning process



20 o VERTEX to VERTEX June 10 1958 c.'A. JARRETT 2,838,365

DRY SPINNING' PROCESS Filed Dec. 21, 1955 2 Sheets-Sheet 1 Figz \ ANGLES so RECMNGLERANGE' ng v VERTEX 1 VERIDEIIQAN'GE RECTANGLE RANGE 1. w

CharIesA.Jal-relf C] I} fi yINZfNTOR. GENERAL RAN6Ef$LOT M W 0EME/vs/o/vs VERTEX By L: W M 05w to /5- I W0 ANGLES 30to130 ATTGRNEYS June 10, 1958 c. A. JARRETT 2,838,365

DgY SPINNING PROCESS Filed Dec. 21, 1955 2 Sheets-Sheet 2 Fig.6 Fig 7 PRIOR ART Charles A.Jarre if INKENTOR.

ATTORNEYS PRIOR ART United States Patent DRY SPINNING PROCESS Charles A. Jarrett, Kingsport, Tenn., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application December 21, 1955, Serial No. 554,587

Claims. (Cl. 18-54) This invention relates to the preparation of. synthetic filaments and fibers from which fabrics may be woven which have unusual scintillating characteristics. More particularly this invention relates to improved dry spinning methods and apparatus for producing from cellulose organic acid ester spinning solutions filaments and fibers of a substantially flat cross-section. This invention also relates to fabrics and other articles of manufacture made of, or containing such flat cross-section filaments and fibers.

Heretofore, special cross-sectional yarns have been obtained by extruding solutions through spinnerettes having various types of rectangular slot orifices. For example, in Hickey Patent 2,373,892 of April 17, 1945, cellulose acetate filaments are formed by dry' spinning a suitable solution through a spinnerette having a plurality of rectangular orifices having a length to width dimension ratioof 1.35 to 1.65. The filaments thus produced have an I-beam cross-section. Other orifices having length to width ratios particularly below :1 have been employed to produce filaments. With the exception of the I-beam fibers these prior art filament yarns may be referred to as crystal yarns. More specifically, filaments spun from a 4:1 rectangular slot will be referred to for purposes of comparison with the filaments of the present invention as standard crystal filaments.

Also Stone Patents 2,000,047 and 2,000,048 describe the method for producing cellulose acetate filaments with a clover-leaf cross-section from round orifices in the spinnerettes. This clover-leaf cross-section is designated for purposes of comparison with the filaments of the pres ent invention as a normal cross-sectional filament. All of the above-mentioned rectangular spinnerette orifices are of conventional rectangular shape, having no modifications, and although the cross-sections of the resulting yarn are somewhat flat, they show an I-beam or dog-bone bulge at each end of the cross-section.

It is an object of this invention to produce a. flat-filament cross-sectional crystal-type yarn that, has no dogbone bulge or l-beam shape on the ends of the fiber crosssection. Although previously prepared crystal yarns how a. scintillating effect when woveninto cloth, it is a further object of this invention to produce a fiber which, when woven into cloth, gives both a greater amount of the scintillating effect and also a different kind of scintillation. This type of scintillation attainable by the present invention is more pronounced and has, a variegated appearance.

Another object of this invention is to provide a process for preparing filaments and fibers of flat-shaped crosssection of the nature hereinafter described.

A further object of this invention is the preparation of the desired filaments and fibers from spinnerette orifices of a simplified design that can be easily and accurately manufactured.

Yet another object of this invention is to. provide a spinnerette having extrusion orifices therein of the shape of an elongated hexagonal slot.

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Previously prepared crystal yarns have caused considerable. difficulty in processing. It appears this difficulty may be caused by the blunt or dog-bone shape of their cross-section. It has also been found that as the length to width ratio of such fiber cross-section increased, processing difficulties also increased. It is therefore. a further object of this invention to make a fiber With improved processability when made with the same crosssectional length to width ratio as the standard crystal yarn.

Other objects. will appear hereinafter.

In accordance with the present invention these and other objects may be attained by forcing a suitable spinning solution through a spinnerette having a plurality of filament forming orifices therein of the cross-sectional shape hereinafter described and drying the resulting filaments in a spinning cabinet under carefully controlled conditions of temperature while subjecting the filaments to predetermined drafting. The temperature of the solution and its rate ofextrusion may also be controlled for optimum results.

The spinnerette orifices employed to form the novel filaments of the. present invention are of an elongated hexagonal shape. These spinnerettes may be formed by adding a similar triangular orifice to each end of a conventional rectangular orifice. The width of the bases of the triangle orifices are. the same as the width of the rectangular orifice. These hexagonal slots are not difficult to manufacture, the punching and broaching each being done in one operation.

Under the optimum conditions of solution temperature and composition, extrusion, drying and drafting, the wet filaments as they leave the orifices temporarily assume a cross-sectional shape corresponding to the hexagonal orifice cross-section. However, in accordance with my invention, by careful control of the extrusion rate, the drafting rate and drying temperatures, there will soon be a change in the filament cross-sections to a substantially flat-shaped cross-section which has no bulges on the sides. Under preferred ranges of operation, as suggested above, and as described in detail further on in this specification, theflat-shaped cross-section will be substantially uniform for each of the simultaneously extruded filaments.

In general the spinnerettes of the present, invention may be employed with any suitable spinning cabinet Such as, for example, one of the general kind described herein. The flat-shaped cross-section filaments can be prepared in accordance with our invention within a satisfactory range of spinning, drafting and solution conditions as is described hereinafter.

The present invention will be further understood by reference to the following detailed description in which several examples of my invention are given and to the related drawings in which:

Fig. 1 is a schematic elevational' view showing a spinning cabinet, and associated apparatus, including a spinnerette whichv has filament forming orifices in the shape of elongated hexagonals positioned near the top of the spinning cabinet with filaments issuing therefrom.

Figs. 2, 3, and 4 are greatly enlarged face views' of spinnerettes showing a plurality of. filament forming orifices having the angular and dimensional limits shown in the legends on the drawing.

Fig. 5 is another enlarged face view of a spinnerette illustrating the overall range in angles and. dimensions of the orifices which may be employed in accordance with the invention. The legends on the drawing further describe the angular and, dimentional limits.

Fig. 6 is a reproduction of a photo-micrograph showing the cross-section of. several fiat-shaped filaments. of the present invention which. are made from hexagonal ori- 3 fices such as shown in Fig. 2 having vertex angles of 60 and a length-to-width ratio of 4:1.

Fig. 7 is a reproduction of a photomicrograph showing the cross-section of several flat-shaped filaments of the present invention which are made from the hexagonal orifices of the type shown in Fig. 3.

Fig. 8 is a reproduction of a photomicrograph showing the cross-section of several flat-shaped filaments of the present invention which are made from the hexagonal and emerging through outlet conduit 26 positioned at a substantial distance below spinnerette 13, as illustrated.

My invention will be further understood by reference to the following examples:

Cellulose acetate in an acetone solution at 28.5% solids, having a viscosity of approximately 1500 poises when measured at C., was extruded in the above dry-spinning apparatus through the following types of hexagonal orifices.

art spinnerette shown in Fig. 9.

The similar parts in the several figures are identified by the same numerals.

Referring to Fig. 1 there is shown schematically a side elevation view of a spinning cabinet 11 and its associated apparatus by which the novel flat-shaped crosssection synthetic filaments and fibers of the instant invention may be manufactured. Mounted at the top of the cabinet is a candle filter unit 12 to which is connected a spinnerette 13 which in accordance with this invention has a plurality of orifices 14 therein which are of hexagonal shape. The face of this novel type of spinnerette 13 with the hexagonal orifices 14 therein is shown in the greatly enlarged view of Fig. 2. The candle filter may be uniformly heated by means of heating coils, not shown, which are positioned so as to surround candle filter 12, and through which coils may be circulated any appropriate heat exchange medium such as water maintained at the desired temperature.

Spinning solution of composition described hereinafter is supplied from conduit 16 through valve 17 to pump 18 which forces the solution at the desired rate to the candle filter unit 12, thence to spinnerette 13 from which it is extruded through the orifices 14 in the form of filaments 25 which initially have a hexagonal cross-section form.

The filaments 25 pass downwardly in the cabinet 11 while progressively losing solvent by evaporation until, in a substantially solidified and dried condition they leave the cabinet 11 and pass around godet roll 20, which is positioned below the lower end of the spinning cabinet 11. As they progress downwardly the filaments change in cross-section from a hexagonal shape to a substantially fiat cross-section as indicated at 25F. Godet role '20 is driven at a uniform speed by means, not shown, to give the desired draft to the filaments 25. From godet roll 20 the filaments pass over the usual guide rolls 21 and are finally wound onto a bobbin 22 after an appropriate twist has been imparted thereto, by means not shown.

To facilitate drying of solvent from the filaments during their travel through the cabinet, heated air is supplied to the cabinet 11 by means of inlet conduits 23 and 24 positioned respectively adjacent the lower and upper ends thereof, the air passing through the cabinet orifices of the type shown in Fig. 4. 10

Rectangu- Type of Triangle Vertex to Cross-see- Rectangular Base Vertex to Vertex lar Base Vertex tional Example Lengt Length/ Length/ Width Base Apex Width Width Width Length Width Length Ratio Ratio Ratio 4:1 60 60 60 5.7:1 8:1 .030 .140 .030 .172 3:1 60 60 60 a 7:1 7:1 .030 .090 .030 .142 2:1 60 60 3.711 6:1 .035 .070 .035 .131 1:1 60 60 60 2. 7:1 4 to 5:1 .040 .060 .040 .100 1:1.6 72 72 36 3. 7:1 .040 .025 .040 .140 3.1:1 30 30 120 3.7:1 .032 .100 .032 .120

All values are given in millimeters.

25 Spinning conditions were as follows: 25; 3 f, if fi gjgg g fl gg g gg g'g gggfijggg Spinning speed 200 meters/minussecfiong filament c g Candlefilter jacket temperatnre C.

Air flow countercurrent. Fig. 10 1s a reproduction of a photomicrograph showo A11 temperature 90 C.

mg the cross-section of several of the dog bone filaments 30 Spinning draft 0.4 to 0.5. -wh1ch were formed by the rectangular cross-scchon prior Total denier 1 50. Total No. of filaments 7.

These are the same spinning conditions that are used to spin the standard crystal yarn with which the yarn of the present invention is favorably compared.

Although only 20 denier-per-filament yarns were spun from the above hexagonal orifices, any denier-per-filament yarn which normally can be spun from a rectangular slot, i. e. 4 to 150 denier per filament, can also be spun from a hexagonal slot. Also the yarn can be prepared in a wide range of dope and spinning conditions.

However, it is preferred that the spinning draft be held below 0.5. This low draft gives the yarn a high elongation, which in turn improves the processability.

Draft may be defined rather broadly as the ratio of the linear velocity of wind-up of the filaments to the linear velocity of extrusion of the spinning solution. More specifically, draft may be defined as the ratio of the linear velocity at which the filaments are wound onto and off the godet roll of a dry spinning cabinet to the calculated average linear velocity at which the quantity of spinning solution necessmy to the formation of any one of the plurality of filaments comprising the bundle of filaments wound onto and off the godet roll is extruded through any one of the plurality of orifices in the spinnerette employed in the spinning operation, the velocities being expressed in the same units of distance per unit time. For example, if the filaments are Wound up at the godet roll at the same linear velocity that the spinning solution is extruded from the spinnerette, the draft is 1.0, thus signifying that the linear speed of wind-up is of the extrusion speed. Similarly, if the filaments are wound up or withdrawn from the cabinet at the godet roll at a linear speed 50% greater than the speed of extrusion, the draft is 1.5, and so on. I

In manufacturing the hexagonal orifices, the triangle can be added to any base rectanglar slot, including a minimum slot length-to-width ratio of .5 :1 and a maximum length-to-width ratio of 15:1. The hexagonal slot can also be made with a variation of triangles on the ends. The vertexes of the slot can have as small an acute angle as 30" or as large an obtuse angle as The filaments produced in accordance with Example 1 are shown in magnified cross-section in Fig. 6. The filaments produced in accordance with Example 5, through the spinnerette shown in Fig. 3, are shown in magnified cross-section in Fig. 7. The filaments produced in accordance with Example 6, through the spinnerette shown in Fig. 4 are shown in magnified cross-section in Fig. 8.

These flat filaments of the instant invention may be contrasted with filaments of similar composition spun under similar conditions through the rectangular spinnerette of the type shown in Fig. 9. The resulting filaments are shown in Fig. 10. It will be noted that the filaments spun through the hexagonal orifices in accordance with the present invention are substantially fiat and have no knobs at the ends of the cross-section. However, those filaments spun through the rectangular orifices are characterized by an uneven surface and do have the undesirable knobs at the ends of the cross-section.

The cross-sections of cellulose acetate fibers when spun from the hexagonal slot have a continuous flat surface from tip to tip, with no dog-bone bulge or I-beam effect on the ends of the cross-section as when spun from a conventional, rectangular slot. When this yarn is woven into cloth, the continual changing of the filaments in the cloth from the flat side to the narrow side and vice versa imparts this scintillating effect to the fabric. To visualize this characteristic, one can imagine the scintillating or glittering efiect that can be seen from a moving twisted ribbon.

I claim:

l. The method of forming cellulose organic acid ester filaments with a flat cross-section, which comprises extruding a cellulose organic acid ester filament forming 1 solution through a. spinnerette equipped with orifices in the form of a hexagon having two parallel sides of equal length and of greater length than the other sides of the hexagon all of which said other sides are of the same length, the vertex angles midway between said parallel sides being equal and within the range of 30 to 130 degrees, drafting the thus formed filaments at a draft ratio within the range of approximately 0.4 to 0.5 while drying the filaments at an average temperature within the range of 60 C. to 90 C. whereby a fiat cross-section filament is produced.

2. The method of forming cellulose organic acid ester filaments with a fiat cross-section, which comprises extruding a cellulose organic acid ester filament formingsolution through a spinnerette equipped with orifices in the form of a hexagon having two parallel sides of equal length and of greater length than the other sides of the hexagon all of which said other sides are of the same length, both the vertex angles midway between said parallel sides being 60 degrees, drafting the thus formed filaments at a draft ratio within the range of approximately 0.4 to 0.5 while drying the filaments at an average temperature within the range of 60 C. to 90 C. whereby a flat cross-section filament is produced.

3. The method of forming cellulose organic acid ester filaments with a flat cross-section, which comprises-extruding a cellulose organic acid ester filament forming solution through a spinnerette equipped with orifices in the form of a hexagon having two parallel sides of equal length and of greater length than the other sides of the hexagon all of which said other sides are of the same length, both the vertex angles midway between said parallel sides being 36 degrees, drafting the thus formed filaments at a draft ratio within the range of approximately 0.4 to 0.5 while drying the filaments at an average temperature within the range of C. to C. whereby a flat cross-section filament is produced.

4. The method of forming cellulose organic acid ester filaments with a flat cross-section, which comprises extruding a cellulose organic acid ester filament forming solution through a spinnerette equipped with orifices in the form of a hexagon having two parallel sides of equal length and of greater length than the other sides of the hexagon all of which said other sides are of the same length, both the vertex angles midway between said parallel sides being degrees, drafting the thus formed filaments at a draft ratio within the range of approximately 0.4 to 0.5 while drying the filaments at an average temperature within the range of 60 C. to 90 C. whereby a flat cross-section filament is produced.

5. The method of forming cellulose acetate filaments with a fiat cross-section, which comprises extruding a cellulose acetate filament forming solution through a spinnerette equipped with orifices in the form of a hexagon having two parallel sides of equal length and of greater length than the other sides of the hexagon all of which said other sides are of the same length, both the vertex angles midway between said parallel sides being equal and within the range of 30 to degrees, drafting the thus formed filaments at a draft ratio within the range of approximately 0.4 to 0.5 while drying the filaments at an average temperature within the range of 60 C. to 90 C. whereby a flat cross-section filament is prm duced.

References Cited in the file of this patent UNITED STATES PATENTS 1,964,659 Brumberger June 26, 1934 2,000,048 Stone May 7, 1935 2,013,688 Kinsella Sept. 10, 1935 2,026,730 Dreyfus Jan. 7, 1936 2,317,485 Rider Apr. 27, 1943 2,387,791 Hoffman Oct. 30, 1945 r 2,612,679 Ladisch Oct. 7, 1952 2,674,025 Ladisch Apr. 6, 1954 2,687,944 Johnson Aug. 31, 1954 2,702,230 Olmer Feb. 15, 1955 2,736,920 Wicker Mar. 6, 1956 2,742,667 Clouzeau Apr. 24, 1956 

1. THE METHOD OF FORMING CELLULOSE ORGANIC ACID ESTER FILAMENTS WITH A FLAT CROSS-SECTION, WHICH COMPRISES EXTRUDING A CELLULOSE ORGANIC ACID ESTER FILAMENT FORMING SOLUTION THROUGH A SPINNERETTE EQUIPPED WITH ORIFICES IN THE FORM OF A HEXAGON HAVING TWO PARALLEL SIDES OF EQUAL LENGTH AND OF GREATER LENGTH THAN THE OTHER SIDES OF THE HEXAGON ALL OF WHICH SAID OTHER SIDES ARE OF THE SAME LENGTH, THE VERTEX ANGLES MIDWAY BETWEEN SAID PARALLEL SIDES BEING EQUAL AND WITHIN THE RANGE OF 30 TO 130 DEGREES, DRAFTING THE THUS FORMED FILAMENTS AT A DRAFT RATIO WITHIN THE RANGE OF APPROXIMATELY 0.4 TO 0.5 WHILE DRYING THE FILAMENTS AT AN AVERAGE TEMPERATURE WITHIN THE RANGE OF 60*C. TO 90*C. WHEREBY A FLAT CROSS-SECTION FILAMENT IS PRODUCED. 